Technical Field
The present invention relates to a liquid discharge apparatus and a head unit.
Related Art
It is known that piezoelectric elements (for example, a piezo element) are used in discharge liquid apparatuses such as ink jet printers which print images and text by discharging ink. The piezoelectric elements are provided to correspond to a plurality of nozzles in a recording head (an ink jet head) and dots are formed by specific amounts of ink (liquid) being discharged at specific timings from the nozzles due to each of the piezoelectric elements being driven in accordance with driving signals. In consideration of electricity, since the piezoelectric elements have a capacitive load such as a capacitor, it is necessary for a sufficient current to be supplied for the piezoelectric elements for each of the nozzles to be operated. For this reason, there is a configuration in the liquid discharge apparatus described above where the piezoelectric elements are driven by a drive circuit supplying driving signals, which are amplified using an amplification circuit, to the head.
For example, in the liquid discharge apparatus such as a serial printer where printing is performed by a carriage which is mounted with the head scanning back and forth, driving signals with high voltages, which are amplified using an amplification circuit which is provided on the main body side of the printer, are typically supplied to the head which is mounted on the carriage via a cable. In this liquid discharge apparatus, it is necessary for the length of the cable to be double or more of the scanning width of the carriage, and there are problems in that the waveforms of the driving signals which are transferred by the cable become distorted and printing quality deteriorates due to the effects of static electricity which is generated due to the cable rubbing against the members inside a casing and various types of external noise such as electrostatic noise which is easily picked up due to the antenna effect with the cable being in the shape of a loop. In particular, as the cable typically becomes longer in large format printers which are able to print onto large sheets of paper such as A2 size or larger, it is easier for the waveforms of the driving signals which are transferred by the cable to become distorted and it is easy for printing quality to deteriorate. With regard to these problems, a liquid discharge apparatus is proposed to reduce the distorting of the driving waveforms due to the effects of noise by also mounting the drive circuit on the carriage along with the head and shortening the transfer path for the driving signals.
For example, Japanese Patent Application Publication No. 2000-343690 discloses a technique for reducing the distorting of the driving waveforms by a drive circuit which uses a class AB amplifier as the amplification circuit being mounted on the carriage. However, power consumption and the amount of heat generation are high due to the large currents flowing through the class AB amplifier, and the size and mounting weight of the carriage is increased due to it being necessary to mount a heat sink for releasing heat on the carriage. As a result, there are problems in that the power consumption of the drive circuit and the power consumption of the motor for scanning the carriage back and forth increase and energy savings and durability of the liquid discharge apparatus deteriorate due to the life of the motor being shortened.
In contrast to this, Japanese Patent Application Publication No. 2014-184586 discloses a technique for reducing the distorting of the driving waveforms by the carriage being mounted with a drive circuit which is able to perform multilevel charging and discharging of the piezoelectric element and to recover and reuse charge which is discharged from the piezoelectric element. In addition, Japanese Patent Application Publication No. 2014-076567 discloses a technique for reducing the distorting of the driving waveforms by the carriage being mounted with a drive circuit which uses a class D amplifier as the amplification circuit. It is possible for the drive circuit which is described in Japanese Patent Application Publication No. 2014-184586 and the drive circuit which is described in Japanese Patent Application Publication No. 2014-076567 to reduce the size and mounting weight of the carriage and improve the energy savings and durability of the liquid discharge apparatus due to the power consumption and the amount of heat generation being smaller than the drive circuit which is described in Japanese Patent Application Publication No. 2000-343690.
The inventors of the present application discovered that, in a case where the weight of the drive circuit which is mounted on the carriage relative to the weight of the head is too large to ignore, there is a difference in the discharge stability of the ink (liquid) and an effect is imparted onto the printing quality due to the mounting position of the drive circuit. However, while the above-mentioned references disclose that the head and the drive circuit are mounted on the carriage as described above, it is not mentioned at what position the drive circuit is to be mounted on the carriage to be able to realize higher printing quality.